In the design and manufacture of a three-dimensional article, it is common practice to first create an initial design of the article and then manually produce a custom prototype or model of the article based upon the initial design. After reviewing the initial design and prototype, design revisions are often made requiring the production of yet another prototype. This process of review and redesign may be repeated a number of times before finding the desired design thereby requiring that a number of preliminary designs and prototypes be produced for a single finished article. Accordingly, the process of designing and prototyping an article may involve considerable time, effort and expense.
Computer aided design (CAD) is commonly used for automating the design process. With the aid of a computer, an operator is able to design a three-dimensional article and display the design on a two-dimensional medium, such as a display screen or paper. In addition, a computer aided milling machine, for example, may be coupled to a CAD system to produce a milled article in response to computer generated CAD data. Unfortunately a milling tool is typically large, expensive and may be limited in the article geometries that may be produced.
Stereolithography is another technology for producing a prototype based upon computer generated coordinate data. An example of stereolithography is disclosed in U.S. Pat. No. 4,575,330 to Hull entitled "Apparatus for Production of Three-Dimensional Objects By Stereolithography." The patent discloses an apparatus producing an article by forming successive cross-sectional laminae of the article at the surface of a fluid medium. The fluid medium is capable of altering its physical state from a fluid to a solid in response to selective stimulation such as by UV radiation; particle bombardment, such as electron beams; chemical reaction; or impinging radiation other than UV radiation. The source of selective stimulation is controlled by a computer in response to computer generated coordinate data.
Stereolithography, however, requires the use of more material than is actually incorporated in the article being produced, and also requires the exact placement of the article being constructed relative to the surface of the fluid medium. The fluids may be toxic and require special handling precautions. In addition, the depth of the layer created when the fluid surface is exposed to the stimulation may be difficult to control, and, accordingly, the resolution of surface features may be difficult to control.
Another apparatus and method for forming three-dimensional articles from a material which is normally solid but flowable when heated is disclosed, for example, in U.S. Pat. No. 5,141,680 to Almquist et al. entitled "Thermal Stereolithography." The apparatus includes a nozzle for dispensing a stream of material which has been heated to the point that it flows. The material is dispensed through the nozzle by applying pressure, and the flow of material can be stopped by a slidable valve or by controlling the pressure. Precise control of the flow of material may be difficult to obtain. Moreover, unsupported portions of the article may be problematic and may collapse unless support is provided. Accordingly, a second support material is provided that must later be removed from the article.
U.S. Pat. No. 5,121,329 to Crump discloses another apparatus wherein a flow of material through a nozzle is used to create a three-dimensional object. In this patent, the flow of material is determined by the size of the outlet orifice, a constant pressure, and the vertical height of the tip of the nozzle. In addition, a spring-loaded ball check valve may assist in metering the flow of material. Again, precise control of this flow may be difficult to obtain, and inaccuracies in the finished article may result.
A significant advance in the art of three-dimensional modeling is disclosed in U.S. Pat. No. 4,665,492 to Masters entitled "Computer Automated Manufacturing Process and System." This patent discloses an apparatus including a repositionable ejection head for ballistically emitting small mass particles or droplets of particulate matter. A machine controller controls a positioner in response to a data file containing coordinate information representing the design of the article being produced. The mass particles are directed to the coordinates of a three-dimensional article as defined by the computer data file, wherein the starting coordinate reference position is described as an origination seed point. The mass particles may include plastic material, a slurry material having water content, charged particles which are electrically deflected, or other materials.
Another method and apparatus for forming three-dimensional solid form objects is disclosed in U.S. Pat. No. 5,257,657 to Gore entitled "Method for Producing A Solid-Phase Object From A Material in the Liquid Phase." According to this patent, droplets of a liquid-phase material are ejected to form a spheroid. As noted in the patent, this method may not work well for glasses and plastics which do not have a set transition temperature at which they become rigid.
Yet another method and apparatus for forming three-dimensional objects is disclosed in U.S. Pat. No. 5,136,515 to Helinski entitled "Method and Means for Constructing Three-Dimensional Articles by Particle Deposition." This patent discloses a device including two jetting heads, or alternately a single jetting head with two feeder lines. In both embodiments, the controller causes fabrication particle material to be ejected as droplets forming the three-dimensional object, while a complementary support structure is created by the ejection of support particles. While this scheme allows the fabrication of layers having various angles, the three-dimensional object must later be separated from the surrounding support material. Accordingly, this device requires the use of more material than is ultimately incorporated in the three-dimensional object. Moreover, two jets and two material supply systems are required, thereby increasing the cost and complexity of the apparatus.
U.S. Pat. No. 5,260,009 to Penn entitled "System, Method, and Process for Making Three-Dimensional Objects" discloses yet another apparatus for forming three-dimensional articles wherein a second or support material is dispensed with each layer of the three-dimensional article as it is formed.
The formation of three-dimensional articles by jetting a photosetting or thermosetting material is disclosed in U.S. Pat. No. 5,059,266 to Yamane et al. entitled "Apparatus and Method for Forming Three-Dimensional Article." A jet sequentially or intermittently jets the photosetting or thermosetting material in a droplet form along a flight path to a stage on which the article is constructed. An exposure unit is then used to cure the deposited material. If a photosetting material is used, the exposure unit is a source of light radiation. A mesh sheet may be required to form an article having a complicated shape.
U.S. Pat. No. 5,140,937 also to Yamane et al. discloses an apparatus for forming a three-dimensional article having plural jets for jetting a thermosetting material and a heat supplying unit for curing the thermosetting material. U.S. Pat. No. 5,149,548, also to Yamane et al., discloses an apparatus for forming a three-dimensional article having a jet head for jetting a two part curable material including microcapsules. This apparatus also includes a microcapsule rupturing unit such as a source of heat, pressure or light radiation. Each of these Yamane et al. patents disclose an apparatus requiring a curing unit to solidify the deposited material.
Other U.S. patents related to three-dimensional modeling are as follows: U.S. Pat. Nos. 5,207,371 to Prinz et al.; 5,301,415 to Prinz et al.; 5,301,863 to Prinz et al.; 5,204,124 to Secretan et al.; 4,749,347 to Valavaara; 5,303,141 to Batchelder et al.; 5,031,120 to Pomerantz et al.; and 5,287,435 to Cohen et al. Despite continuous development in the area of rapid prototype modelling, there is still a need for an apparatus and fabrication methods to quickly and inexpensively make arbitrary three-dimensional articles with a high degree of accuracy.